Tensioning rails are used in large numbers for various applications in internal combustion engines, both for the timing chain drive of the engine and for driving auxiliary units, e.g. the oil pump. In the case of timing chain drives as well as auxiliary drives a tensioning rail can hold the drive chain at a defined tension and compensate the elongation of the chain occurring due to manufacturing tolerances and wear. Tensioning rails are normally pivotably supported on a bearing pin provided at a bearing point that is fixedly connected to the engine block, and they are pretensioned against the drive chain via an actively operated tensioning device or a passively acting spring unit.
DE 100 143 33 A1 discloses a tensioning rail for a chain drive, in the case of which a torsion coil spring is arranged, in the area of its coiled portion, around a sleevelike pivot of the tensioning rail. Whereas one end of the coil spring rests in a hole of the engine block, the other end of the tensioning rail presses against the drive chain. Another tensioning rail pretensioned by means of a torsion coil spring is known from DE 44 37 926 C1, the tensioning rail of the auxiliary drive being here supported on a guide rail of the associated main drive. DE 43 27 314 A1, however, describes a chain tensioner with a leaf spring supported at one end thereof, the leaf spring being provided with a sliding body and being under a constant pretension with respect to the drive chain. Reference DE 10 2004 014 486 A1 shows again a pivotably supported tensioning rail with a torsion coil spring arranged on the bearing pin, said torsion coil spring resting on a counter bearing, which is fixedly arranged relative to the bearing pin, so as to press the tensioning rail against the drive chain.
Modern internal combustion engines comprise an increasing number of units to be driven, the installation space available for the engine remaining the same or getting even smaller. In addition, modern engines get more and more complex so as to fulfil the stricter statutory provisions with respect to exhaust gas emission and fuel consumption.
The increasing number of auxiliary units, in combination with the higher complexity of the internal combustion engines, leads to a reduction of the possibilities of arranging necessary drives as well as tensioning and guide rails associated therewith. It follows that, for installing pivotably supported tensioning rails, complicated or unusual structural designs are sometimes necessary, which often entail new problems with respect to wear resistance and operational reliability.
Although many of the prior art tensioning devices based on the use of tensioning rails proved to be very useful, it is, especially due to the strong competition in the field of automotive industry, continuously endeavored to optimize tensioning rails and their incorporation into engine constructions that get more and more complicated. In addition, tensioning rails are mass-produced articles for the automotive industry, which, with respect to the high number of pieces and the progressive innovation in this field, continuously underlie the necessity to replace the constructions used by simpler and less expensive concepts.
It is therefore the object of the present invention to provide a tensioning rail, which, avoiding the drawbacks of known constructions, can be manufactured and mounted at a reasonable price and is easy to use in spite of the increased complexity of modern engine constructions.